Particle Model of Matter | AQA GCSE Physics | Topic 3

• density = mass/volume
• The particle model: solids are dense so particles are close together and vibrate about a fixed position. in liquids, particles are furtherr apart and move around slowly. gases are less dense so particles are further apart, and move at random speeds in random directions.
• Changes of state are physical changes, not chemical changes, and mass is conserved.
• Internal energy: the total kinetic and potential energy stored by particles.
• Heating a system will cause a rise in internal energy (temperature) or a change of state. Not both at the same time.

• E = mCAT (given in equation sheet)
• E - mL (given in equation sheet)
• Specific heat capacity: the energy needed to raise the temperature of 1kg by 1^o C.
• Specific latent heat: the energy needed to change state of 1kg of a substance.
• Fusion: solid to liquid. Vaporisation: liquid to vapour.
• Gas molecules are in constant random motion. The temperature is related to the average kinetic energy of the molecules.
• Increasing the temperature, at a fixed volume, increases the pressure exerted by the gas (because it will bump into walls of the container with more force).

Separate Science Physics Students Only

• old pressure x old volume = new pressure x new volume
• Work done is energy transferred by a force.
• Doing work on a gas increases the internal energy and can cause an increase in temperature.